In this page we discuss a critical step in setting up a
digital
darkroom:
calibrating your monitor so it conforms to widely-accepted standards of
image display. A properly calibrated monitor is essential for making
prints
that match the monitor image; it is an absolute
necessity for success in the digital darkroom. Printer
calibration is now on a separate page.

This page makes little mention of color
management-- a set of tools and
techniques that enable you
to achieve optimum monitor/print matching and make prints with
nonstandard
inks and papers. You don't need it to get started. It involves a
learning
curve, but it's simple to use once you've mastered it. Otherwide it's
error-prone.
I now use a fully color-managed workflow.

Color
management Sooner or later you'll have to
face it if you
want to make the finest possible prints.

Setting
up your monitor

Your monitor should be operated in subdued light; strong direct light
should
not reach the screen. Dark areas of the screen should appear dark to
the
eye. I work in a semi-darkened room with a lamp to the left of my
screen
(positoned so no direct light reaches the screen). Total darkness is
unnecessary.
CreativePro.com has nice articles about ambient
light and viewing
lights.

Set your monitor's color temperature (white point) to 6500K, D65, or
sRGB,
which is equivalent to 6500K. This is preferable to setting it on video
card or monitor calibration
software. My
monitor
selections are 5000K (D50), 6500K (D65), and 9300K. Older monitors with
no color temperature setting default to around 9000-9300K, which is far
too blue to comfortably match prints viewed under incandescent light,
which
has color temperatures between 2600 and 4200K. The 5000K setting
appears
too dull and yellow on most CRT monitors.

.
Note the confusing terminology: Artists call higher color temperatures
(bluer) "cooler" and lower color temperatures (yellower) "warmer." The
huge variety of available hardware can make setting color temperature
confusing.
You may have the option of setting color temperature on the monitor
(preferred)
or with video card or monitor
calibration software. Do not set it in both;
this
may
result in an overcorrection-- your monitor will appear dim and yellow.
Software settings work correctly if the monitor is uncorrected, i.e.,
about
9000-9300K. Unless you have a calibrator
you'll
have to trust your eyes: White and gray images (where R = G = B) should
appear tonally neutral, i.e., they should have no visible tint. The Gamma
and monitor
test patterns are
excellent
for this purpose.

Your display adaptor software should be set to 24
or 32 bit color
(True
Color). To see the setting, right-click on the Windows wallpaper (the
background
outside any open windows), then click on Properties,
Settings.

I
use a SoLuxDesk
Task Lamp with a 4700K 36 degree 50W bulb for viewing prints.
(Thanks, Luca
Salgarelli.) The SoLux has a CRI (color rendering index) of 0.98.
CRI is a measure of how accurately a light source can render color. 100
is maximum; 90 is OK. I purchased it from www.lightbulbsdirect.com
(click here
for the Desk Lamp). At the 6500K monitor setting, a white sheet of
paper
viewed under the SoLux lamp looks a tiny bit yellower (warmer) than
white
areas on the monitor screen. This is not a problem since the eye adapts
quickly when moving from the monitor to the print. The SoLux color
temperature
is actually quite close to the monitor; much closer than a halogen
lamp.
It has an orange cast on the periphery, which some users may find
annoying.

Alternative lamps: Two promising choices are Ott-Lite's
18W VisionSaverTM
series, which has a color temperature of about 5300K and CRI = 0.95,
and Sunwave
5500K fluorescent bulbs, which come in both tubes and compact screw-in
models, have good brightness and CRI = 0.93. The Philips 287813 15 watt
screw-in daylight compact fluorescent bulb:
5000K, CRI = 0.82, is available at Home
Depot, SKU #652746, about $15. It's quite bright. Other
compact
fluorescents: SunPro,
Panasonic,
and Verilux.

I keep a halogen desk lamp nearby to see what the print will look like
in typical indoor lighting.

Set the Contrast to maximum unless the image is too bright or harsh.

Adjust gamma,
the parameter that
describes
the nonlinear relationship between image pixels and monitor brightness,
and Brightness (black level)
using the Gamma
and black level chart, below. Several procedures
are abailable. There is some interaction between brightness and gamma
adjustments,
so you may have to go back and forth between them.

Digital
Dog's test image should look
good, though
I find the skin tones to be somewhat cool (very slightly blue) on my
monitor.
The image of the dog (center; the digital descendant of Victor's
"Nipper")
should appear neutral gray except for the few specks of color. You may
want to look at other calibration images, such as the Robyn
Color calibration scan.

Monitors are specified by their diagonal length.
Standard sizes are
14, 15, 17, 19 and 21 inches. But there's a rub: CRT manufacturers cheat in
specifying the diagonal size! The use the outside dimensions
of the picture tube. The opening you see is one inch
less than
the
specified monitor dimensions. My Hitachi 19 inch
monitor is 18
inches diagonally. LCD specs are more honest.

You should set your monitor's horizontal and
vertical size adjustments
for about 0.1 inch margins-- about as large as you can without cutting
off the edges. Image sizes are shown in the table below.

You
should set screen resolution for between 72
and 100 pixels per inch.
If you set it for less than 72 pixels per inch, you won't be making use
of your monitor's capabilities-- your image will have less detail than
it should. If you set it for more than 100 dpi, you may be sending more
detail than your monitor or eyes can resolve. To adjust screen
resolution,
right-click on the Windows wallpaper (the background outside any open
windows),
then click on Properties,
Settings.
Suggested monitor resolution settings are shown in the table below--
recommendations
are in boldface (the higher resolution, 90+ ppi, is
for younger
eyes).

Specified
monitorsize
(inches)

Horizontal(inches)

Vertical(inches)

Recommendedresolution

Pixelsper
inch

14

10.2

7.6

800x600

78

15

11.0

8.2

800x6001024x768

7393

17

12.6

9.4

1024x7681152x864

8191

19

14.2

10.6

1024x7681152x8641280x960

728190

21

15.8

11.8

1280x9601600x1200

81101

I
recommend at least a 17 inch monitor and at least 1024x768
resolution. If you increase resolution and fonts are too small, you can
adjust them by right-clicking on the Windows wallpaper, then clicking
on Properties,
Appearance. Details
depend on the operating system.

Test
images

A good
test image is useful for evaluating your monitor's
quality and
calibration as well as the match between the monitor and printer. I
found
a nice image on The Digital Dog's website. Go to http://www.digitaldog.net/tips/index.shtml
and shift-click or right-click on Printer
Test File. Winzip (or a similar utility) must be
installed on your system to
turn this file, whose default name is Printer
Test file.jpg.zip,
into a JPEG. The 1600x2000
pixel
image,
shown greatly reduced on the right, includes a portrait with good skin
tones, color and grayscale step charts, and the Gretag
Macbeth® ColorChecker color rendition chart. (Bruce
Lindbloom hasColorChecker RGB
values for various color spaces-- sRGB, Adobe 1998, etc.; Babelcolor
(Danny Pascale) has an outstanding description of the
ColorChecker.) While you're at Digital Dog's site, check out his many
excellent articles and tutorials.

[Color management
information:
The file has an embedded ICC profile tag for Apple ColorMatch color
space
(gamma = 1.8). In non-ICC aware applications, or in ICC-aware
applications
with color management turned off, this tag is simply ignored. No
problem.
But if you are using color management you must be aware of it. You
should
use an ICC printer profile rather than Color Controls settings, as
described
below. Why? Because when color management is enabled, there is a
translation
between the file color space and the monitor (display) color space.
Other
files, without profiles or with different profiles, translate
differently.
The Color Controls settings ignore the profiles-- no translation takes
place; the relationship between print and monitor appearance won't be
consistent.
But all will be well if you use an ICC printer profile (that's what
they're
for). I don't recommend converting to another color space, though
simply
removing the profile tag doesn't do much damage (the Gretag Macbeth
Colorcheker
displays slightly dark).]

Another standard test image (below, right) originated with
PhotoDisc,
Inc., which has been absorbed into Getty
Images (no connection with the Getty
Museum). They have a nice page of articles
on color theory and management. A 10 MB (large)
high quality JPEG of this image can be downloaded from Inkjetart.com--
one of my favorite sources of printing materials. The image size is 3225x5055
pixels. The colors are unsaturated (far from Velvia), apparently
because
the file data is for the Adobe RGB (1998) color space (see Color
management for an explanation of color spaces), but the file
contains
no embedded Adobe RGB (1998) profile. (Also, most web browsers do not
recognize
profiles-- they assume all images are in the default sRGB color space.)

[Color
management
information:
The file (PDI-Target.jpg) has no embedded ICC profile tag. The file
data
is apparently
for Adobe
RGB 1998. That's why colors appear unsaturated in web browsers and
image
editors that assume sRGB file data. To get proper appearance-- correct
saturation-- in a color
managed
workflow,
you must add an ICC profile tag without changing the image data. In
Picture
Window Pro, you do this by clicking Transformation,
Color, Change
Color Profile..., then setting New
Color Profile: to SMPTE-240M
(or Adobe RGB,
which is identical)
and Change: to Profile
Setting Only (not
the default).]

...An
excellent
opportunity to
collect high quality photographic prints and support this website

.

Gamma
and black level

Gamma
describes the nonlinear relationship between the pixel levels in your
computer
and the luminance of your monitor (the light energy it emits) or the
reflectance
of your prints. The equation is,

Luminance =
C
* valuegamma +
black level

C is set by the
monitor Contrast
control.
Value
is the pixel level normalized to a maximum of 1.
For an 8 bit
monitor
with pixel levels 0 - 255, value
= (pixel
level)/255. Black
level is
set
by the (misnamed) monitor Brightness control. The relationship is
linear
if gamma = 1.
The chart on the
right
illustrates the relationship for gamma = 1, 1.5, 1.8 and 2.2 with C
= 1 and black level
= 0.

Gamma affects middle tones; it has no effect on black or
white. If
gamma
is set too high, middle tones appear too dark. Conversely, if it's set
too low, middle tones appear too light. [Note: Film is different. Gamma
increases with development time; highlights are strongly affected.]

Gamma, as defined above, is also called display
gamma-- the product of monitor's
native gamma and video
card lookup table
(LUT)
gamma.
(Most video cards have LUTs.) As we shall see, it is closely related to
film
gamma, which is the average slope of
the film
response curve.

Black level
is the monitor luminance or print reflectance for value
= pixel level =
0; i.e., it is the
deepest black in the monitor or print. It is a constant that includes
the
effects of viewing flare (stray light).
In good
monitor
viewing environments it can be very small, less than 0.01, relative to
a normalized maximum Luminance of 1. It's also around 0.01 for high
quality
prints (higher for mediocre paper/ink combinations). Sometimes
black level appears inside the exponent, but it makes little difference
since it's a constant.

Geeks
only! The correct gamma equation for sRGB
color space

The
simplified, ideal equation for the sRGB color space (the standard color
space of Windows and the Web; gamma = 2.2) is

y = x2.2, where y is the luminance and
x is the
normalized
pixel level.

The
curves for the two equations are very close, as illustrated here.
The correct curve is linear below x = 0.03928, y = 0.003035. This
corresponds
to a pixel level of 10 for images with a bit depth of 8, where the
maximum
pixel level is 255. For the ideal curve at pixel level = 10, y = 0.0008
(much lower). The difference is even more striking at pixel level = 5
(x
= 0.0196): y = 0.00152 for the correct equation; y = 0.000175 for the
ideal
curve. This has consequences for setting the black level.

[Obscure
note: the two links above give different values of
x for the
boundary
between the linear and exponential curves: 0.03928 and 0.04045. Annyoing,
but the equations are nearly identical because the slopes of the two
curves
are very close around x = 0.04.]

Why gamma?

The
eye doesn't respond linearly to light; it responds to relative
brightness
or luminance differences. The
smallest luminance
difference the eye can distinguish in bright light (Delta L)
is
expressed by the Weber-Fechner law,

Delta L/L
= 0.01 = 1%

(G. Wyszecki & W. S. Stiles,
"Color Science,"
Wiley, 1982, pp. 567-570). Most video cards display 8
bits per
color
(256 levels), even if you store and edit in 16 bits per color channel.
With gamma = 1, the relative luminance difference at the highest
luminance
levels would be less than 0.004 (1/256)-- much less than the eye can
distinguish,
but it increases rapidly for lower levels. In dark areas it can be
large
enough to cause perceptible banding between levels. This can be
corrected
by applying a gamma curve, as illustrated in the graph on the right,
which
shows the
relative luminance difference between pixel levels
for
gamma = 1, 1.5, 1.8, and 2.2. The relative difference is most
consistent
for gamma = 2.2. It remains under 0.01 at high brightness levels, but
it
is lower than gamma = 1 for luminances under 0.2.

Relative differences are
not displayed
uniformly
when luminance is plotted on a linear scale, but they are on logarithmic
scales: relative differences such as doubling or halving the luminance
(changing it by one exposure zone) occupy the same distance,
independently
of the absolute level.

A
deeper insight into the meaning of gamma can be gained by looking at a
logarithmic plot of Luminance vs. Pixel level.
If we take the logarithm of both sides of the luminance equation,
above,
and neglect black level (set it to zero), the equation becomes log(Luminance)
= log(C * valuegamma)
= log(C)
+
gamma * log(value).In
a logarithmic plot, gamma becomes the slope of a straight line,
as illustrated on the left for gamma = 1 and 2.2. Now compare this plot
to photographic paper, on the right.

For
photographic film and paper, gamma is defined at the average slope of
the
response curve in its linear region. As we can see in this diagram for
Kodak Polymax photographic paper, higher contrast corresponds to a
steeper
slope-- higher gamma. In comparing these two plots, note that the
independent
variable, Log10(Exposure) corresponds to Log10(Pixel
level), while Log10(Luminance) corresponds to -Density.
(Both slopes are positive because the paper is a negative
material.)
One unit on a Log10 scale (such as Density)
equals 3.32
exposure
zones (f-stops); one exposure zone equals 0.301 Density units.

Comparing these
two plots should make it clear
that gamma in film is essentially the same as gamma in monitors: it is
the
slope
of the characteristic curve that relates Density (-Log10(Luminance))
to the independent variable. In other words,

Gamma
is contrast.

The Contrast
control on monitors and
television
sets is actually brightness, and the Brightness control is, as we've
seen,
black level. The nomenclature is
confusing but deeply
entrenched.
In television sets operating in typical viewing conditions, where high
ambient light limits the visible dynamic range, the Contrast control
affects
the
apparent contrast.

The native gamma of monitors-- the relationship between grid
voltage
and luminance-- is typically around 2.5, though it can vary
considerably.
This is well above any of the display standards, so you must
be aware of gamma and correct it.

A display
gamma of 2.2
is
the
de facto standard for the Windows operating system
and the
Internet-standard
sRGB
color space. The standard for Mcintosh and prepress file interchange is
1.8. Video cameras have gammas of approximately 0.45-- the inverse of
2.2.
The viewing or
system
gamma is the product of the gammas of
all the devices in
the system-- the image acquisition device (film+scanner or digital
camera),
color lookup table (LUT), and monitor. System gamma is typically
between
1.1 and 1.5. Viewing flare and other factor make images look flat at
system
gamma = 1.0. To learn more, go to links.

.

Gamma
and black level chart

The
chart below
enables you to set the black level (brightness) and estimate display
gamma
over a range of 1 to 3 with precison better than ±0.1. The
gamma
pattern is on the left; the black level pattern is on the right. Before
using the chart, the
monitor should be turned for on at least 15
minutes (30 preferred). For flat screen (LCD) monitors, Screen
resolution (right-click on the wallpaper, Properties, Settings) should
be set to the monitor's native resolution.

Gamma
is estimated by locating the position where the average luminance
across
the gamma pattern is constant. The corresponding gamma is shown on the
left. You should be far enough from your monitor so the line pattern is
not clearly visible. The example below shows what to look for. The
solid
areas are calculated from the equation,

pixel
level = 255*luminance(1/gamma) ;
luminance
= 0.5.

This
chart
features gradual
density changes along horizontal scan lines (thus eliminating risetime
problems). It allows more precise gamma estimation than most
traditional
charts. I encourage you to download it and check it occasionally.

What
to look for(for
Gamma = 2.0)

Your
monitor's
gamma should be 2.2 or 1.8.

2.2 is recommended for
Windows, the Internet sRGB
color space, and the popular Adobe RGB (1998) color space. 1.8 is the
standard
for older Macintosh systems and prepress file interchange (Mac users,
see note below). I
aim for gamma = 2.2. Most laptop LCD screens are
poorly suited
for critical image editing because gamma is extremely sensitive to
viewing
angle.

I'll
be happy to grant permission to reproduce it on your website if you e-mail
me, give me credit and a link to this page.

Black
level (brightness) Your
monitor's
brightness control (which should actually be called black level) can be
adjusted using the mostly black pattern on the right side of the chart.
This pattern contains two dark gray vertical bars, A and B, which
increase
in luminance with increasing gamma. (If you can't see them, your black
level is way low.) The left bar (A) should be just
above the
threshold
of visibility opposite your chosen gamma (2.2 or 1.8)-- it should be
invisible
where gamma is lower by about 0.3. The right bar (B) should be
distinctly
visible: brighter than (A), but still very dark.

There
is considerable interaction between the brightness
and gamma settings--
increasing brightness decreases gamma-- so you may
have to go
back
and forth two or three times. There is less interaction between
Contrast
and gamma. The vertical bars correspond to normalized luminances of
0.002
and 0.006 at the specified gamma.

Monitor
test patterns

The patterns on the right
represent an ultimate
test of monitor quality and calibration. If your monitor is functioning
properly and calibrated to gamma = 2.2 or 1.8, the corresponding
pattern
will appear smooth neutral gray when viewed from a distance. Any
waviness, irregularity, or color banding indicates incorrect monitor
calibration
or poor performance. You will see irregularities if the black level
(brightness
control) is set too low, causing dark areas clip, if the monitor
saturates
in bright areas (a sign of old age), or if your monitor is
malfunctioning
in any way. The optimum black level settng is typically a little higher
than the lowest level where smoothness can be achieved. This setting
should
be consistent with the gamma chart instructions, above.

You
can learn a lot by running QuickGamma, below, and observing the
interaction
between its gamma adjustment and the black level adjustment on your
monitor.
There may be little you can do to make this pattern look good on laptop
LCD monitors, but modern high-quality flat screen monitors should be
fine.

I
recommend that you check this
pattern whenever
you adjust or calibrate your monitor. You might want to download it and
display it in your image editor-- it's a quick way to diagnose problems.

The
popular GretagMacbeth
ColorChecker can
also be used as a check of monitor calibration. The simulated image on
the left has an embedded sRGB color space-- the Windows/Internet
standard,
with gamma = 2.2. The patch values were calculated by Bruce Lindbloom.

For
Macintosh users

I'm not a
Mac expert,
but I've heard that the recommended gamma setting has changed from 1.8
(in the old days) to 2.2. These changes are mentioned in LCD
Display Calibration by Ian Lyons. The following paragraphs
were
contributed by Julian Vrieslander. I'm not sure if they're up to date.

If your
web browser is Internet
Explorer for Macintosh, version 5.0 or later, you should disable
ColorSync
color management before using the chart. This option is found
in
the Preferences settings: Preferences > Web Content > Use
ColorSync.
If the box is checked, clear it and reload the page. Colorsync can't be
disabled in the Safari (OS X) web brower.

With "Use
ColorSync " on,
the chart indicated gamma = 2.2 on a system calibrated for gamma = 1.8
with a Colorvision Monitor Spyder and OptiCAL 3.5 software. With " Use
ColorSync" off, the correct gamma (1.8) is displayed. For Netscape
Communicator
4.7.7 for Classic Mac OS, which doesn't have a color management option,
the chart shows gamma = 1.8.

Setting
gamma

To
calibrate your monitor, i.e., to adjust gamma with any of
the following
techniques, your video card should have a Lookup
Table (LUT).
Most recent video cards have one. QuickGamma
displays a pop-up message if no LUT is found. If your video card
doesn't
have one, it's ancient; replace it with a new one. It doesn't have to
be
expensive or fast. 8 MB is the minimum video memory. 16 MB is faster
for
switching between screens. Most cards have more.

There are
two basic approaches to adjusting gamma: the Visual
approach, which uses a special pattern, and the Calibrator
approach, which uses a colorimeter or "SpyderTM."
The
ColorVision
Spyder is shown on the right. The two approaches are compared in the
table
below.

Approach

Visual

Calibrator

Advantages

It's
free! And it can do a good job of
calibrating most
monitors.

Extremely
accurate. Produces
monitor profiles for use with color-managed workflows.

Programs

QuickGamma
(below):
an excellent little utility. Recommended. Adobe
Gamma:
included
with Photoshop.Monica:
a nice Linux utility.Video
card software:
doesn't require the installation of a new program, but can be
inconvenient.

Can
achieve
excellent results
if your monitor is well-behaved, i.e., if its luminance is proportional
to (pixel level)gamma_native. If its response is
irregular--
due to aging or malfunction-- you'll need a calibrator (or a new
monitor).

Can
achieve
excellent results
with a wider range of monitors-- the curves entered in the LUT can be
more
complex than the simple exponentials used with the Visual approach.

You can set your
monitor
to 6500K (or sRGB, which is 6500K), but accuracy may be poor. This is
rarely
a major issue because the eye adapts when it moves from the monitor to
the print, which is typically displayed at 5000K or lower. If the Monitor
test pattern appears to be neutral gray on the monitor, it's
fine;
you'll be able to match prints. If it has a color tint you'll need to
get
a calibrator (or a new monitor).

You can
calibrate the monitor's
white point to exactly 6500K. This is not a major advantage. See
comments
on the left.

Best
for color
management
because you'll get a monitor profile that represents the true
performance
of your monitor (which is close to sRGB for typical CRTs).

If you are
starting out I recommend
the visual
approach. It's fast, simple, and provides good results in most cases. QuickGamma
is a particularly nice little Windows utility for visual calibration. (Monica
is a comparable Linux program.) You can
verify
its accuracy with the Monitor
test
pattern. If
it is smooth neutral gray when viewed from a distance, your monitor is
well-calibrated and can't be improved by much.

If you want the ultimate in monitor-print
matching or
you can't
get good calibration with the visual approach, get
a calibrator
and upgrade to a color-managed
workflow. Luminous-Landscape.com
and many other authors strongly recommend this approach. But the
improvement
over the visual approach may be modest because the Windows-default sRGB
color space is close to typical CRT monitors calibrated for gamma =
2.2.

My friend Miles
Hecker recommends
the ColorVision
SpyderPROTM with OptCALTM
package, which
sells
for $249 US. OptiCAL software is excellent and the new Spyder has seven
filters instead of the usual three-- it is a true colorimeter, i.e., it
can measure the human eye's response to color. This probably makes
little
difference for CRTs, all of which have similar phosphor responses, but
it can be advantageous in calibrating LCD monitors, which can have very
different spectral responses. By 2005 virtually all new monitors will
be
LCDs: they've gotten very good and new production
capacity will
drop the cost below CRTs.

Calibration
and profiling: the source of the confusion(for
color-managed workflows only)

An
image can be altered in two
places on the way to the monitor. (1) by the video lookup table (LUT).
This is performed by all
the calibration
techniques below. (2) by gamut
mapping
in color-managed
workflows, performed by the color engine (CMM) under the control of an
ICC monitor profile.
See Color
management parts 1:
Introduction
and 2:
Implementation for
more detail.

The
LUT is normally loaded with values that enable the display to operate
at
the gamma (usually 2.2) specified by the calibration
process.

Confusion
arises because both
transformations take place in color-managed workflows, and both are
controlled
by an ICC monitor profile. An ICC profile provides data for the LUT
loader
program, which is run at startup; it also provides information for the
gamut mapping between the working color space and the monitor color
space.
To confuse things further, Photoshop uses the Windows default monitor
profile
while Picture Window Pro uses a user-selected monitor profile.

This
page focuses on calibration.

QuickGamma
(visual)

Eberhard Werle of Laatzen, Germany
(near Hannover)
has written a excellent gamma calibration utility called QuickGamma
2.0 that runs on all versions of Windows starting
with 98. (Monica
is a comparable Linux program.)
The 437 kB installation program, QuickGammaV2EN.exe
(new version with bug fix, October 2004)
can be downloaded by clicking here.
Running it installs QuickGamma.exe (the main program),
QuickGammaLoader.exe
(the program that loads the LUT at Windows start), QuickGamma.chm (the
help file), and two files for easy uninstallation (using the Windows
Control
Panel). The program is also available from Eberhard's QuickGamma
site. German
and French
versions can be accessed by clicking on the appropriate flag. Although
English isn't Eberhard's native language, the Help file is clear and
concise.
If you have questions or suggestions, Eberhard's e-mail address is in
the
Help file and on the site.

The right portion of
the QuickGamma dialog box is shown on the
right.
The left portion, which consists of my gamma
chart,
is used to calibrate gamma and to adjust black level, which interacts
with
gamma. When you first load it, the gamma doesn't change. You have to
click
on one of the spin buttons (the up or down-arrows to the right of the
Gamma
box) to load QuickGamma's settings in the LUT. The number in the Gamma
box increases as displayed gamma (on the chart) decreases: it indicates
the monitor's native (uncorrected) gamma when the monitor is corrected
to display gamma = 2.2. Version 2.0 has an option for individually
adjusting
gamma for Red, Green, and Blue. Unlike the color management packages
(above),
QuickGamma doesn't create a monitor profile. It stores the LUT values
in
the Windows Registry. Check the Run
QuickGamaLoader at Windows Startup box if
you'd like the
calibration values to be loaded whenever you reboot the computer.

This is
an outstanding little
program.
I strongly recommend it if you don't have a calibrator. If your monitor
is healthy
it can achieve excellent calibration, which you can verify with the Monitor
test pattern.

Another
open-source program named QuickGamma,
written by ydnar of Shaderlab,has
no connection with
Eberhard's program.

The
first program packages in the table below can take advantage
of
calibrators to create ICC monitor profiles. This is essential if you
have
a color-managed workflow. Adobe Gamma (which has to be run from the
Control
panel) creates a rough ICC profile, based on answers to questions about
gamma, white point, and CRT phosphors. Quick Gamma doesn't produce a
profile.
Calibrators have been reviewed by Macworld and Dry Creek Photo.

The following comments apply to the programs than
create ICC monitor profiles.

Run the calibration program, following the
instructions. The ICC
monitor profiles are used by their respective loader programs
to
calibrate
the monitor. Give the profile a unique name, for example,
Monitor_120203.icm.
It is placed in the Windows profile directory. You may be asked whether
you want to make it the Windows
default
monitor
profile. In most cases the answer is
"yes."

The loader program uses data in the Windows
default
monitor profile to set the video card lookup table (LUT).
When
any
of the program packages is installed, the loader program is placed in
the
Startup directory so it runs whenever the computer is booted. You can
also
run the loader program manually.

Conflicts can arise when more than one loader
program may be present
in the Startup directory. To see the contents of the startup directory,
run the System
Configuration
Utility by clicking Start,
Run...,
and entering
msconfig
in the
Open
box.
Click on the Startup
tab. Only one loader program should be checked. This is a good time for
a little system cleanup. Uncheck unneeded resource-hungry programs such
as Microsoft's evil FindFast. Some sources of
advice: Answers
that work | Pacman's
Portal Start Up Tips (which has an impressive list
of startup programs).

To view or change the Windows
default monitor profile, open the Display
Properties screen by right-clicking on the
Windows
wallpaper
(background) and clicking on Properties
or by opening the Control
Panel
and clicking on Display.
Then click on Settings,
Advanced...,
Color
Management. The Default Monitor Profile and a
set of
profiles
currently associated with the monitor are shown. You can add profiles
to
the list or set any of them as the Default.

Warning
on generic monitor profiles
There
are
some that will cause you nothing but headaches in an ICC-aware
application.
An example is the profile for the Sony
CPD-G520 21" CRT monitor. If you go to their Monitor
/ Display Support web page and download the driver for the
CPD-G520,
you'll find a nice looking profile called Sony_d65.icm. A Trojan horse!
Its TRC curves are set for gamma = 2.5; it can get you into serious
trouble.
More details can be found in Color
management:
implementation.

Setting
gamma with the video card software (visual)

This
technique works for most video cards, but t's not my first choice. I
prefer
QuickGamma.
The dialog box on the right is for the Matrox MGA-G200 AGP video card,
which is pretty typical. Open the Display
Properties screen by right-clicking on the Windows
wallpaper
(the
background outside any open windows) and clicking on Properties,
or by opening the Control
Panel
and
clicking on Display.
Click on Settings,
Advanced...,
Color.
The default setting (which you can get by clicking on Reset)
is a straight line (R, G, B sliders centered). Click the Link
box so that all sliders move together. Display the gamma chart (above)
on your monitor, then adjust the sliders for the desired gamma (2.2 for
Windows). It's best to set your monitor to 6500K (or D65 or sRGB) and
leave
the Color temperature
slider
centered
(its default). Setting gamma with my new ATI Radeon video
card
(which
replaed the Matrox after it was fried in a power surge) is difficult
because
it doesn't allow the three (R, G, and B) sliders to be linked.

If gamma for the three color channels (R, G, and B) is
inconsistent,
you'll notice color variation across the chart (it should be uniform
neutral
gray). You may be able to correct it by unchecking Link
and adjusting the sliders separately. This can be tricky because the B
slider is hard to judge. The detailed charts in Background
to calibration can help diagnose problems.

A source of confusion: some software indicates a
default gamma of
1.0.
This is not actual viewing
gamma; it is gamma
correction.
If you use this value you'll get the monitor's default gamma, typically
around 2.5 for CRTs. The LUT loader programs described above will
override
these settings at startup.

Images
and text copyright (C) 2000-2013 by Norman Koren. Norman Koren lives
in Boulder, Colorado, where he worked in developing magnetic recording
technology for high capacity data storage systems until 2001. Since 2003 most of his time has been devoted to the development of Imatest. He has been involved with photography since 1964.